Process for preparing carboxylic acids

ABSTRACT

This invention relates to a process for preparing carboxylic acids by oxidizing an aldehyde with a peracid in the presence of an amine and/or amine N-oxide catalyst selected from the group consisting of a substituted or unsubstituted alkyl amine, alkyl amine N-oxide, aromatic amine, aromatic amine N-oxide, heterocyclic amine, heterocyclic amine N-oxide and mixtures thereof, to produce the carboxylic acid. Such carboxylic acids have utility for example as chemical intermediates.

BRIEF SUMMARY OF THE INVENTION RELATED APPLICATIONS

The following are related, commonly assigned applications filed on aneven date herewith: U.S. patent application Ser. No. 545,349 and U.S.patent application Ser. No. 547,702, both of which are incorporatedherein by reference.

TECHNICAL FIELD

This invention relates to a process for preparing carboxylic acids byoxidizing an aldehyde with a peracid in the presence of an amine and/oramine N-oxide catalyst to produce the carboxylic acid.

BACKGROUND OF THE INVENTION

Various processes for oxidizing an aldehyde with a peracid to produce acarboxylic acid have been described in the art. However, there is acontinuing need to provide improved processes for preparing carboxylicacids by oxidizing an aldehyde with a peracid to produce the carboxylicacids in which the amount of formate byproducts is reduced or eliminatedand the oxidation efficiency is enhanced.

DISCLOSURE OF THE INVENTION

This invention relates to a process for producing a carboxylic acidwhich process comprises oxidizing an aldehyde with a peracid in thepresence of an amine and/or amine N-oxide catalyst selected from thegroup consisting of a substituted or unsubstituted alkyl amine, alkylamine N-oxide, aromatic amine, aromatic amine N-oxide, heterocyclicamine, heterocyclic amine N-oxide and mixtures thereof, to produce thecarboxylic acid, wherein said amine and/or amine N-oxide catalyst has abasicity sufficient to catalyze said oxidizing of the aldehyde to thecarboxylic acid, and provided that when the peracid is performic acid,the aldehyde is other than an aromatic or heteroaromatic aldehyde.

This invention also relates to a process for producing a carboxylic acidwhich process comprises: (1) reacting an olefinically unsaturatedcompound with carbon monoxide and hydrogen in the presence of ametal-ligand complex catalyst to produce an aldehyde; and (2) oxidizingthe aldehyde with a peracid in the presence of an amine and/or amineN-oxide catalyst selected from the group consisting of a substituted orunsubstituted alkyl amine, alkyl amine N-oxide, aromatic amine, aromaticamine N-oxide, heterocyclic amine, heterocyclic amine N-oxide andmixtures thereof, to produce the carboxylic acid, wherein said amineand/or amine N-oxide catalyst has a basicity sufficient to catalyze saidoxidizing of the aldehyde to the carboxylic acid, and provided that whenthe peracid is performic acid, the aldehyde is other than an aromatic orheteroaromatic aldehyde.

This invention further relates to a process for producing a carboxylicacid which process comprises: (1) reacting an olefinically unsaturatedorganic compound with carbon monoxide and hydrogen in the presence of arhodium-ligand complex catalyst to produce an aldehyde; and (2)oxidizing the aldehyde with a peracid in the presence of an amine and/oramine N-oxide catalyst selected from the group consisting of asubstituted or unsubstituted alkyl amine, alkyl amine N-oxide, aromaticamine, aromatic amine N-oxide, heterocyclic amine, heterocyclic amineN-oxide and mixtures thereof, to produce the carboxylic acid, whereinsaid amine and/or amine N-oxide catalyst has a basicity sufficient tocatalyze said oxidizing of the aldehyde to the carboxylic add, andprovided that when the peracid is performic acid, the aldehyde is otherthan an aromatic or heteroaromatic aldehyde.

DETAILED DESCRIPTION Aldehyde-Forming Reaction

The aldehyde employed in the process of this invention can be preparedby conventional methods known in the art. The preferred aldehyde-formingreaction is a hydroformylation reaction. The hydroformylation reactioninvolves the production of aldehydes by reacting an olefinic compoundwith carbon monoxide and hydrogen in the presence of a solubilizedmetal-organophosphorus complex catalyst and free organophosphorus ligandin a liquid medium that also contains a solvent for the catalyst andligand. The process may be carried out in a continuous single pass modein a continuous gas recycle manner or more preferably in a continuousliquid catalyst recycle manner as described below. The hydroformylationprocessing techniques employable herein may correspond to any knownprocessing techniques employed in conventional hydroformylationreactions.

The hydroformylation reaction mixture starting materials employableherein includes any organic solution derived from any correspondinghydroformylation process that contains at least some amount of fourdifferent main ingredients or components, i.e., the aldehyde product, ametal-organophosphorus ligand complex catalyst, free organophosphorusligand and an organic solubilizing agent for said catalyst and said freeligand, said ingredients corresponding to those employed and/or producedby the hydroformylation process from whence the hydroformylationreaction mixture starting material may be derived. By "free ligand" ismeant organophosphorus ligand that is not complexed with (tied to orbound to) the metal, e.g., rhodium atom, of the complex catalyst. It isto be understood that the hydroformylation reaction mixture compositionsemployable herein can and normally will contain minor amounts ofadditional ingredients such as those which have either been deliberatelyemployed in the hydroformylation process or formed in situ during saidprocess. Examples of such ingredients that can also be present includeunreacted olefin starting material, carbon monoxide and hydrogen gases,and in situ formed type products, such as saturated hydrocarbons and/orunreacted isomerized olefins corresponding to the olefin startingmaterials, and high boiling liquid aldehyde condensation by-products, aswell as other inert co-solvent type materials or hydrocarbon additives,if employed.

In an embodiment of this invention, certain additives can be employed inthe hydroformylation reaction mixture to stabilize the organophosphorusligands against degradation. For example, epoxides can be added to thehydroformylation reaction mixture to reduce degradation of theorganophosphite ligand as described in U.S. Pat. No. 5,364,950, thedisclosure of which is incorporated herein by reference.

The catalyst useful in the hydroformylation reaction includes ametal-ligand complex catalyst. The permissible metals which make up themetal-ligand complexes include Group VIII metals selected from rhodium(Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni),palladium (Pd), platinum (Pt), osmium (Os) and mixtures thereof, withthe preferred metals being rhodium, cobalt, iridium and ruthenium, morepreferably rhodium, cobalt and ruthenium, especially rhodium. Otherpermissible metals include Group IB metals selected from copper (Cu),silver (Ag), gold (Au) and mixtures thereof, and also Group VIB metalsselected from chromium (Cr), molybdenum (Mo), tungsten (W) and mixturesthereof, and also Group VA metals selected from arsenic (As) andantimony (Sb) and mixtures thereof. Mixtures of metals from Group VIII,Group IB, Group VIB and Group VA may be used in this invention. Thepermissible organophosphorus ligands which make up the metal-ligandcomplexes include organophosphines, e.g., triorganophosphines, andorganophosphites, e.g., mono-, di-, tri- and polyorganophosphites. Otherpermissible organophosphorus ligands include, for example,organophosphonites, organophosphinites, organophosphorus amides and thelike. Mixtures of such ligands may be employed if desired in themetal-ligand complex catalyst and/or free ligand and such mixtures maybe the same or different. This invention is not intended to be limitedin any manner by the permissible organophosphorus ligands or mixturesthereof. It is to be noted that the successful practice of thisinvention does not depend and is not predicated on the exact structureof the metal-ligand complex species, which may be present in theirmononuclear, dinuclear and/or higher nuclearity forms. Indeed, the exactstructure is not known. Although it is not intended herein to be boundto any theory or mechanistic discourse, it appears that the catalyticspecies may in its simplest form consist essentially of the metal incomplex combination with the ligand and carbon monoxide when used.

The term "complex" as used herein and in the claims means a coordinationcompound formed by the union of one or more electronically richmolecules or atoms capable of independent existence with one or moreelectronically poor molecules or atoms, each of which is also capable ofindependent existence. For example, the ligands employable herein, i.e.,organophosphorus ligands, may possess one or more phosphorus donoratoms, each having one available or unshared pair of electrons which areeach capable of forming a coordinate covalent bond independently orpossibly in concert (e.g., via chelation) with the metal. Carbonmonoxide (which is also properly classified as a ligand) can also bepresent and complexed with the metal. The ultimate composition of thecomplex catalyst may also contain an additional ligand, e.g., hydrogenor an anion satisfying the coordination sites or nuclear charge of themetal. Illustrative additional ligands include, e.g., halogen (Cl, Br,I), alkyl, aryl, substituted aryl, acyl, CF₃, C₂ F₅, CN, (R)₂ PO andRP(O)(OH)O (wherein each R is the same or different and is a substitutedor unsubstituted hydrocarbon radical, e.g., the alkyl or aryl), acetate,acetylacetonate, SO₄, PF₄, PF₆, NO₂, NO₃, CH₃ O, CH₂ =CHCH₂, C₆ H₅ CN,CH₃ CH, NO, NH₃, pyridine, (C₂ H₅)₃ N, mono-olefins, diolefins andtriolefins, tetrahydrofuran, and the like. It is of course to beunderstood that the complex species are preferably free of anyadditional organic ligand or anion that might poison the catalyst andhave an undue adverse effect on catalyst performance. It is preferred inthe metal-ligand complex catalyzed hydroformylation reactions that theactive catalysts be free of halogen and sulfur directly bonded to themetal, although such may not be absolutely necessary. Preferredmetal-ligand complex catalysts include rhodium-organophosphine ligandcomplex catalysts and rhodium-organophosphite ligand complex catalysts.

The number of available coordination sites on such metals is well knownin the art. Thus the catalytic species may comprise a complex catalystmixture, in their monomeric, dimeric or higher nuclearity forms, whichare preferably characterized by at least one phosphorus-containingmolecule complexed per one molecule of metal, e.g., rhodium. As notedabove, it is considered that the catalytic species of the preferredcatalyst employed in the hydroformylation reaction may be complexed withcarbon monoxide and hydrogen in addition to the organophosphorus ligandsin view of the carbon monoxide and hydrogen gas employed by thehydroformylation reaction.

Among the organophosphines that may serve as the ligand of themetal-organophosphine complex catalyst and/or free organophosphineligand of the hydroformylation reaction mixture starting materials aretriorganophosphines, trialkylphosphines, alkyldiarylphosphines,dialkylarylphosphines, dicycloalkylarylphosphines,cycloalkyldiarylphosphines, triaralkylphosphines,tricycloalkylphosphines, and triarylphosphines, alkyl and/or arylbiphosphines and bisphosphine mono oxides, as well as ionictriorganophosphines containing at least one ionic moiety selected fromthe salts of sulfonic acid, of carboxylic acid, of phosphonic acid andof quaternary ammonium compounds, and the like. Of course any of thehydrocarbon radicals of such tertiary non-ionic and ionicorganophosphines may be substituted if desired, with any suitablesubstitutent that does not unduly adversely affect the desired result ofthe hydroformylation reaction. The organophosphine ligands employable inthe hydroformylation reaction and/or methods for their preparation areknown in the art.

Illustrative triorganophosphine ligands may be represented by theformula: ##STR1## wherein each R¹ is the same or different and is asubstituted or unsubstituted monovalent hydrocarbon radical, e.g., analkyl or aryl radical. Suitable hydrocarbon radicals may contain from 1to 24 carbon atoms or greater, the most preferred hydrocarbon radicalbeing phenyl, (C₆ H₅ --). Illustrative substituent groups that may bepresent on the aryl radicals include, e.g., alkyl radicals, alkoxyradicals, silyl radicals such as --Si(R²)₃ ; amino radicals such as--N(R²)₂ ; acyl radicals such as --C(O)R² ; carboxy radicals such as--C(O)OR² ; acyloxy radicals such as --OC(O)R² ; amido radicals such as--C(O)N(R²)₂ and --N(R²)C(O)R² ; ionic radicals such as --SO₃ M whereinM represents inorganic or organic cationic atoms or radicals; sulfonylradicals such as --SO₂ R² ; ether radicals such as --OR² ; sulfinylradicals such as --SOR² ; sulfenyl radicals such as --SR² as well ashalogen, nitro, cyano, trifluoromethyl and hydroxy radicals, and thelike, wherein each R² individually represents the same or differentsubstituted or unsubstituted monovalent hydrocarbon radical, with theproviso that in amino substituents such as --N(R²)₂, each R² takentogether can also represent a divalent bridging group that forms aheterocyclic radical with the nitrogen atom and in amido substituentssuch as C(O)N(R²)₂ and --N(R²)C(O)R² each --R² bonded to N can also behydrogen. Illustrative alkyl radicals include, e.g., methyl, ethyl,propyl, butyl and the like. Illustrative aryl radicals include, e.g.,phenyl, naphthyl, diphenyl, fluorophenyl, difluorophenyl,benzoyloxyphenyl, carboethoxyphenyl, acetylphenyl, ethoxyphenyl,phenoxyphenyl, hydroxyphenyl; carboxyphenyl, trifluoromethylphenyl,methoxyethylphenyl, acetamidophenyl, dimethylcarbamylphenyl, tolyl,xylyl, and the like.

Illustrative specific organophosphines include, e.g.,triphenylphosphine, tris-p-tolyl phosphine,tris-p-methoxyphenylphosphine, tris-p-fluorophenylphosphine,tris-p-chlorophenylphosphine, tris-dimethylaminophenylphosphine,propyldiphenylphosphine, t-butyldiphenylphosphine,n-butyldiphenylphosphine, n-hexyldiphenylphosphine,cyclohexyldiphenylphosphine, dicyclohexylphenylphosphine,tricyclohexylphenylphosphine, tribenzylphosphine as well as the alkaliand alkaline earth metal salts of sulfonated triphenylphosphines, e.g.,of (tri-m-sulfophenyl)phosphine and of (m-sulfophenyl)diphenyl-phosphineand the like. The most preferred organophosphine ligands aretriphenylphosphine (TPP) and the sodium salt of3-(diphenylphosphino)benzene sulfonic acid (TPPMS-Na), while the mostpreferred catalysts are a rhodium-TPP complex and a rhodium-TPPMS-Nacomplex.

More particularly, illustrative metal-organophosphine complex catalytsand illustrative free organophosphine ligands include, e.g., thosedisclosed in U.S. Pat. Nos. 3,527,809; 4,148,830; 4,247,486; 4,283,562;4,400,548; 4,482,749 and 4,861,918, the disclosures of which areincorporated herein by reference.

Among the organophosphites that may serve as the ligand of themetal-organophosphite complex catalyst and/or free organophosphiteligand of the hydroformylation reaction mixture starting materials aremonoorganophosphites, diorganophosphites, triorganophosphites andorganopolyphosphites. The organophosphite ligands employable in thisinvention and/or methods for their preparation are known in the art.

Representative monoorganophosphites may include those having theformula: ##STR2## wherein R³ represents a substituted or unsubstitutedtrivalent hydrocarbon radical containing from 6 to 18 carbon atoms orgreater, such as trivalent acyclic and trivalent cyclic radicals, e.g.,trivalent alkylene radicals such as those derived from1,2,2-trimethylolpropane and the like, or trivalent cycloalkyleneradicals such as those derived from 1,3,5-trihydroxycyclohexane, and thelike. Such monoorganophosphites may be found described in greaterdetail, e.g., in U.S. Pat. No. 4,567,306, the disclosure of which isincorporated herein by reference.

Representative diorganophosphites may include those having the formula:##STR3## wherein R⁴ represents a substituted or unsubstituted divalenthydrocarbon radical containing from 4 to 40 carbon atoms or greater andW represents a substituted or unsubstituted monovalent hydrocarbonradical containing from 1 to 18 carbon atoms or greater.

Representative substituted and unsubstituted monovalent hydrocarbonradicals represented by W in the above formula (III) include alkyl andaryl radicals, while representative substituted and unsubstituteddivalent hydrocarbon radicals represented by R⁴ include divalent acyclicradicals and divalent aromatic radicals. Illustrative divalent acyclicradicals include, e.g., alkylene, alkylene-oxy-alkylene,alkylene-NX-alkylene wherein X is hydrogen or a substituted orunsubstituted monovalent hydrocarbon radical, alkylene-S-alkylene, andcycloalkylene radicals, and the like. The more preferred divalentacyclic radicals are the divalent alkylene radicals such as disclosedmore fully, e.g., in U.S. Pat. Nos. 3,415,906 and 4,567,302 and thelike, the disclosures of which are incorporated herein by reference.Illustrative divalent aromatic radicals include, e.g., arylene,bisarylene, arylene-alkylene, arylene-alkylene-arylene,arylene-oxy-arylene, arylene-NX-arylene wherein X is as defined above,arylene-S-arylene, and arylene-S-alkylene, and the like. More preferablyR⁴ is a divalent aromatic radical such as disclosed more fully, e.g., inU.S. Pat. Nos. 4,599,206 and 4,717,775, and the like, the disclosures ofwhich are incorporated herein by reference.

Representative of a more preferred class of diorganophosphites are thoseof the formula: ##STR4## wherein W is as defined above, each Ar is thesame or different and represents a substituted or unsubstituted arylradical, each y is the same or different and is a value of 0 or 1, Qrepresents a divalent bridging group selected from --C(R⁵)₂ --, --O--,--S--, --NR⁶ --, Si(R⁷)₂ -- and --CO--, wherein each R⁵ is the same ordifferent and represents hydrogen, alkyl radicals having from 1 to 12carbon atoms, phenyl, tolyl, and anisyl, R⁶ represents hydrogen or amethyl radical, each R⁷ is the same or different and represents hydrogenor a methyl radical, and m is a value of 0 or 1. Such diorganophosphitesare described in greater detail, e.g., in U.S. Pat. Nos. 4,599,206 and4,717,775, the disclosures of which are incorporated herein byreference.

Representative triorganophosphites may include those having the formula:##STR5## wherein each R⁸ is the same or different and is a substitutedor unsubstituted monovalent hydrocarbon radical, e.g., an alkyl or arylradical. Suitable hydrocarbon radicals may contain from 1 to 24 carbonatoms or greater and may include those described above for R¹ in formula(I).

Representative organopolyphosphites contain two or more tertiary(trivalent) phosphorus atoms and may include those having the formula:##STR6## wherein X¹ represents a substituted or unsubstituted n-valenthydrocarbon bridging radical containing from 2 to 40 carbon atoms, eachR⁹ is the same or different and is a divalent hydrocarbon radicalcontaining from 4 to 40 carbon atoms, each R¹⁰ is the same or differentand is a substituted or unsubstituted monovalent hydrocarbon radicalcontaining from 1 to 24 carbon atoms, a and b can be the same ordifferent and each have a value of 0 to 6, with the proviso that the sumof a+b is 2 to 6 and n equals a+b. Of course it is to be understood thatwhen a has a value of 2 or more, each R⁹ radical may be the same ordifferent, and when b has a value of 1 or more, each R¹⁰ radical mayalso be the same or different.

Representative n-valent (preferably divalent) hydrocarbon bridgingradicals represented by X¹, as well as representative divalenthydrocarbon radicals represented by R⁹ above, include both acyclicradicals and aromatic radicals, such as alkylene, alkylene-Qm-alkylene,cycloalkylene, arylene, bisarylene, arylene-alkylene, andarylene-(CH₂)_(y) -Qm-(CH₂)_(y) -arylene radicals, and the like, whereinQ, m and y are as defined above for formula (IV). The more preferredacyclic radicals represented by X¹ and R⁹ above are divalent alkyleneradicals, while the more preferred aromatic radicals represented by X¹and R⁹ above are divalent arylene and bisarylene radicals, such asdisclosed more fully, e.g., in U.S. Pat. Nos. 3,415,906; 4,567,306;4,599,206; 4,769,498; 4,717,775; 4,885,401; 5,202,297; 5,264,616 and5,364,950, and the like, the disclosures of which are incorporatedherein by reference. Representative monovalent hydrocarbon radicalsrepresented by each R¹⁰ radical above include alkyl and aromaticradicals.

Illustrative preferred organopolyphosphites may include bisphosphitessuch as those of formulas (VII) to (IX) below: ##STR7## wherein each R⁹,R.sup. 10 and X¹ of formulas (VII) to (IX) are the same as defined abovefor formula (VI). Preferably, each R⁹ and X¹ represents a divalenthydrocarbon radical selected from alkylene, arylene,arylene-alkylene-arylene, and bisarylene, while each R¹⁰ represents amonovalent hydrocarbon radical selected from alkyl and aryl radicals.Phosphite ligands of such formulas (VI) to (IX) may be found disclosed,e.g., in said U.S. Pat. Nos. 4,668,651; 4,748,261; 4,769,498; 4,885,401;5,202,297; 5,235,113; 5,254,741; 5,264,616; 5,312,996; 5,364,950; and5,391,801; the disclosures of all of which are incorporated herein byreference.

Representative of more preferred classes of organobisphosphites arethose of the following formulas (X) to (XII): ##STR8## wherein Ar, Q,R⁹, R¹⁰, X¹, m and y are as defined above. Most preferably X¹ representsa divalent aryl-(CH₂)_(y) -(Q)_(m) -(CH₂)_(y) -aryl radical wherein eachy individually has a value of 0 or 1; m has a value of 0 or 1 and Q is--C(R⁵)₂ -- wherein each R⁵ is the same or different and represents ahydrogen or methyl radical. More preferably each alkyl radical of theabove defined R¹⁰ groups may contain from 1 to 24 carbon atoms and eacharyl radical of the above-defined Ar, X¹, R⁹ and R¹⁰ groups of the aboveformulas (VI) to (XII) may contain from 6 to 18 carbon atoms and saidradicals may be the same or different, while the preferred alkyleneradicals of X¹ may contain from 2 to 18 carbon atoms and the preferredalkylene radicals of R⁹ may contain from 5 to 18 carbon atoms. Inaddition, preferably the divalent Ar radicals and divalent aryl radicalsof X¹ of the above formulas are phenylene radicals in which the bridginggroup represented by --(CH₂).sub. y--(Q)_(m) --(CH₂)_(y) -- is bonded tosaid phenylene radicals in positions that are ortho to the oxygen atomsof the formulas that connect the phenylene radicals to their phosphorusatom of the formulae. It is also preferred that any substituent radicalwhen present on such phenylene radicals be bonded in the para and/orortho position of the phenylene radicals in relation to the oxygen atomthat bonds the given substituted phenylene radical to its phosphorusatom.

Moreover, if desired any given organophosphite in the above formulas(VI) to (XII) may be an ionic phosphite, i.e., may contain one or moreionic moieties selected from the group consisting of:

SO₃ M wherein M represents inorganic or organic cationic atoms orradicals,

PO₃ M wherein M represents inorganic or organic cationic atoms orradicals,

N(R¹¹)₃ X² wherein each R¹¹ is the same or different and represents ahydrocarbon radical containing from 1 to 30 carbon atoms, e.g, alkyl,aryl, alkaryl, aralkyl, and cycloalkyl radicals, and X² representsinorganic or organic anionic atoms or radicals,

CO₂ M wherein M represents inorganic or organic cationic atoms orradicals,

as described, e.g., in U.S. Pat. Nos. 5,059,710; 5,113,022 and5,114,473, the disclosures of which are incorporated herein byreference. Thus, if desired, such phosphite ligands may contain from 1to 3 such ionic moieties, while it is preferred that only one such ionicmoiety be substituted on any given aryl moiety in the phosphite ligandwhen the ligand contains more than one such ionic moiety. As suitablecounter-ions, M and X², for the anionic moieties of the ionic phosphitesthere can be mentioned hydrogen (i.e. a proton), the cations of thealkali and alkaline earth metals, e.g., lithium, sodium, potassium,cesium, rubidium, calcium, barium, magnesium and strontium, the ammoniumcation and quaternary ammonium cations. Suitable anionic atoms ofradicals include, for example, sulfate, carbonate, phosphate, chloride,acetate, oxalate and the like.

Of course any of the R⁹, R¹⁰, X² and Ar radicals of such non-ionic andionic organophosphites of formulas (VI) to (XII) above may besubstituted if desired, with any suitable substituent containing from 1to 30 carbon atoms that does not unduly adversely affect the desiredresult of the hydroformylation reaction. Substituents that may be onsaid radicals in addition of course to corresponding hydrocarbonradicals such as alkyl, aryl, aralkyl, alkaryl and cyclohexylsubstituents, may include for example silyl radicals such as --Si(R¹²)₃; amino radicals such as --N(R¹²)₂ ; phosphine radicals such as-aryl-P(R¹²)₂ ; acyl radicals such as --C(O)R¹² ; acyloxy radicals suchas --OC(O)R¹² ; amido radicals such as --CON(R¹²)₂ and --N(R¹²)COR¹² ;sulfonyl radicals such as --SO₂ R¹² ; alkoxy radicals such as --OR¹² ;sulfinyl radicals such as --SOR¹² ; sulfenyl radicals such as --SR¹² ;phosphonyl radicals such as --P(O)(R¹²)₂ ; as well as, halogen, nitro,cyano, trifluoromethyl, hydroxy radicals, and the like, wherein each R¹²radical is the same or different and represents a monovalent hydrocarbonradical having from 1 to 18 carbon atoms (e.g., alkyl, aryl, aralkyl,alkaryl and cyclohexyl radicals), with the proviso that in aminosubstituents such as --N(R¹²)₂ each R¹² taken together can alsorepresent a divalent bridging group that forms a heterocyclic radicalwith the nitrogen atom, and in amido substituents such as --C(O)N(R¹²)₂and --N(R¹²)COR¹² each R¹² bonded to N can also be hydrogen. Of courseit is to be understood that any of the substituted or unsubstitutedhydrocarbon radicals groups that make up a particular givenorganophosphite may be the same or different.

More specifically illustrative substituents include primary, secondaryand tertiary alkyl radicals such as methyl, ethyl, n-propyl, isopropyl,butyl, sec-butyl, t-butyl, neo-pentyl, n-hexyl, amyl, sec-amyl, t-amyl,iso-octyl, decyl, octadecyl, and the like; aryl radicals such as phenyl,naphthyl and the like; aralkyl radicals such as benzyl, phenylethyl,triphenylmethyl, and the like; alkaryl radicals such as tolyl, xylyl,and the like; alicyclic radicals such as cyclopentyl, cyclohexyl,1-methylcyclohexyl, cyclooctyl, cyclohexylethyl, and the like; alkoxyradicals such as methoxy, ethoxy, propoxy, t-butoxy, --OCH₂ CH₂ OCH₃,--(OCH₂ CH₂)₂ OCH₃, --(OCH₂ CH₂)₃ OCH₃, and the like; aryloxy radicalssuch as phenoxy and the like; as well as silyl radicals such as--Si(CH₃)₃, --Si(OCH₃)₃, --Si(C₃ H₇)₃, and the like; amino radicals suchas --NH₂, --N(CH₃)₂, --NHCH₃, --NH(C₂ H₅),and the like; arylphosphineradicals such as --P(C₆ H₅)₂, and the like; acyl radicals such as--C(O)CH₃, --C(O)C₂ H₅, --C(O)C₆ H₅, and the like; carbonyloxy radicalssuch as --C(O)OCH₃ and the like; oxycarbonyl radicals such as --O(CO)C₆H₅, and the like; amido radicals such as --CONH₂, --CON(CH₃)₂,--NHC(O)CH₃, and the like; sulfonyl radicals such as --S(O)₂ C₂ H₅ andthe like; sulfinyl radicals such as --S(O)CH₃ and the like; sulfenylradicals such as --SCH₃, --SC₂ H₅, --SC₆ H₅, and the like; phosphonylradicals such as --P(O)(C₆ H₅)₂, --P(O)(CH₃)₂, --P(O)(C₂ H₅)₂, -P(O)(C₃H₇)₂, --P(O)(C₄ H₉)₂, --P(O)(C₆ H₁₃)₂, --P(O)CH₃ (C₆ H₅), --P(O)(H)(C₆H₅), and the like.

Specific illustrative examples of organobisphosphite ligands include,e.g., the following:

2-t-butyl-4-methoxyphenyl(3,3'- di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite having the formula: ##STR9##6,6'- 3,3, '-bis(1,1-dimethylethyl)-5,5'-dimethoxy-1,1'-biphenyl!-2,2'-diyl!bis(oxy)!bis-dibenzo d,f! 1,3,2!dioxaphosphepinhaving the formula: ##STR10## 6,6'- 3,3',5,5'-tetrakis(1,1-dimethylpropyl)-1,1'-biphenyl!-2,2'-diyl!bis(oxy)!bis-dibenzo d,f! 1,3,2!dioxaphosphepinhaving the formula: ##STR11## 6,6'- 3,3',5,5'-tetrakis(1,1-dimethylethyl)-1,1'-biphenyl!-2,2'-diyl!bis(oxy)!bis-dibenzo d,f! 1,3,2!dioxaphosphepinhaving the formula: ##STR12## 6- 2'-(4,6-bis(1,1-dimethylethyl)-1,3,2-benzodioxaphosphol-2-yl)oxy!-3,3'-bis(1,1-dimethylethyl)-5,5'-dimethoxy1,1'-biphenyl!-2-yl!oxy!-4,8-bis(1,1-dimethylethyl)-2,10-dimethoxydibenzod,f! 1,3,2!dioxaphosphepin having the formula: ##STR13## 6- 2'-1,3,2-benzodioxaphosphol-2yl)oxy!-3,3'-bis(1,1-dimethylethyl)-5,5'-dimethoxy1,1'-biphenyl!-2-yl!oxy!-4,8-bis(1,1-dimethylethyl)-2,10-dimethoxy-dibenzod,f! 1,3,2!dioxaphosphepin having the formula: ##STR14## 6- 2'-(5,5-dimethyl-1,3,2-dioxaphosphorinan-2-yl)oxy!-3,3'-bis(1,1-dimethylethyl)-5,5'-dimethoxy1,1'-biphenyl!-2-yl!oxy!-4,8-bis(1,1-dimethylethyl)-2,10-dimethoxydibenzod,f! 1,3,2!dioxaphosphepin having the formula: ##STR15## 2'- 4,8-bis(1,1-dimethylethyl)-2,10-dimethoxydibenzo- d,f!1,3,2!dioxaphosphepin-6-yl!oxy!-3,3'-bis(1,1-dimethylethyl)-5,5'-dimethoxy1,1'-biphenyl!-2-yl bis(4-hexylphenyl)ester of phosphorous acid havingthe formula: ##STR16## 2- 2- 4,8,-bis(1,1-dimethylethyl),2,10-dimethoxydibenzo d,f!1,3,2!dioxophosphepin-6-yl!oxy!-3-(1,1-dimethylethyl)-5-methoxyphenyl!methyl!-4-methoxy,6-(1,1-dimethylethyl)phenyldiphenyl ester of phosphorous acid having the formula: ##STR17##3-methoxy-1,3-cyclohexamethylene tetrakis3,6-bis(1,1-dimethylethyl)-2-naphthalenyl!ester of phosphorus acidhaving the formula: ##STR18## 2,5-bis(1,1-dimethylethyl)-1,4-phenylenetetrakis 2,4-bis(1,1-dimethylethyl)phenyl!ester of phosphorous acidhaving the formula: ##STR19## methylenedi-2,1-phenylene tetrakis2,4-bis(1,1-dimethylethyl)phenyl!ester of phosphorous acid having theformula: ##STR20## 1,1'-biphenyl!-2,2'-diyl tetrakis2-(1,1-dimethylethyl)-4-methoxyphenyl!-ester of phosphorous acid havingthe formula: ##STR21##

The metal-organophosphorus ligand complex catalysts employable in thisinvention may be formed by methods known in the art. For instance,preformed metal hydrido-carbonyl-organophosphorus ligand catalysts maybe prepared and introduced into the reaction mixture of ahydroformylation process. More preferably, the metal-organophosphorusligand complex catalysts can be derived from a metal catalyst precursorwhich may be introduced into the reaction medium for in situ formationof the active catalyst. For example, rhodium catalyst precursors such asrhodium dicarbonyl acetylacetonate, Rh₂ O₃, Rh₄ (CO)₁₂, Rh₆ (CO)₁₆,Rh(NO₃)₃ and the like may be introduced into the reaction mixture alongwith the organophosphorus ligand for the in situ formation of the activecatalyst. In a preferred embodiment of this invention, rhodiumdicarbonyl acetylacetonate is employed as a rhodium precursor andreacted in the presence of a solvent with the organophosphorus ligand toform a catalytic rhodium-organophosphorus ligand complex precursor whichis introduced into the reactor along with excess free organophosphorusligand for the in situ formation of the active catalyst. In any event,it is sufficient for the purpose of this invention that carbon monoxide,hydrogen and organophosphorus compound are all ligands that are capableof being complexed with the metal and that an activemetal-organophosphorus ligand catalyst is present in the reactionmixture under the conditions used in the hydroformylation reaction.

More particularly, a catalyst precursor composition can be formedconsisting essentially of a solubilized metal-organophosphorus ligandcomplex precursor catalyst, an organic solvent and free organophosphorusligand. Such precursor compositions may be prepared by forming asolution of a metal starting material, such as a metal oxide, hydride,carbonyl or salt, e.g. a nitrate, which may or may not be in complexcombination with a organophosphorus ligand as defined herein. Anysuitable metal starting material may be employed, e.g. rhodiumdicarbonyl acetylacetonate, Rh₂ O₃, Rh₄ (CO)₁₂, Rh₆ (CO)₁₆, Rh(NO₃)₃,and organophosphorus ligand rhodium carbonyl hydrides. Carbonyl andorganophosphorus ligands, if not already complexed with the initialmetal, may be complexed to the metal either prior to or in situ duringthe carbonylation process.

By way of illustration, the preferred catalyst precursor composition ofthis invention consists essentially of a solubilized rhodium carbonylorganophosphorus ligand complex precursor catalyst, an organic solventand free organophosphorus ligand prepared by forming a solution ofrhodium dicarbonyl acetylacetonate, an organic solvent and aorganophosphorus ligand as defined herein. The organophosphorus ligandreadily replaces one of the dicarbonyl ligands of the rhodiumacetylacetonate complex precursor at room temperature as witnessed bythe evolution of carbon monoxide gas. This substitution reaction may befacilitated by heating the solution if desired. Any suitable organicsolvent in which both the rhodium dicarbonyl acetylacetonate complexprecursor and rhodium organophosphorus ligand complex precursor aresoluble can be employed. The amounts of rhodium complex catalystprecursor, organic solvent and organophosphorus ligand, as well as theirpreferred embodiments present in such catalyst precursor compositionsmay obviously correspond to those amounts employable in thehydroformylation process of this invention. Experience has shown thatthe acetylacetonate ligand of the precursor catalyst is replaced afterthe hydroformylation process has begun with a different ligand, e.g.,hydrogen, carbon monoxide or organophosphorus ligand, to form the activecomplex catalyst as explained above. The acetylacetone which is freedfrom the precursor catalyst under hydroformylation conditions is removedfrom the reaction medium with the product aldehyde and thus is in no waydetrimental to the hydroformylation process. The use of such preferredrhodium complex catalytic precursor compositions provides a simpleeconomical and efficient method for handling the rhodium precursor metaland hydroformylation start-up.

Accordingly, the metal-organophosphorus ligand complex catalysts used inthe process of this invention consists essentially of the metalcomplexed with carbon monoxide and a organophosphorus ligand, saidligand being bonded (complexed) to the metal in a chelated and/ornon-chelated fashion. Moreover, the terminology "consists essentiallyof", as used herein, does not exclude, but rather includes, hydrogencomplexed with the metal, in addition to carbon monoxide and theorganophosphorus ligand. Further, such terminology does not exclude thepossibility of other organic ligands and/or anions that might also becomplexed with the metal. Materials in amounts which unduly adverselypoison or unduly deactivate the catalyst are not desirable and so thecatalyst most desirably is free of contaminants such as metal-boundhalogen (e.g., chlorine, and the like) although such may not beabsolutely necessary. The hydrogen and/or carbonyl ligands of an activemetal-organophosphorus ligand complex catalyst may be present as aresult of being ligands bound to a precursor catalyst and/or as a resultof in situ formation, e.g., due to the hydrogen and carbon monoxidegases employed in hydroformylation process of this invention.

As noted the hydroformylation reactions involve the use of ametal-organophosphorus ligand complex catalyst as described herein. Ofcourse mixtures of such catalysts can also be employed if desired. Theamount of metal-organophosphorus ligand complex catalyst present in thereaction medium of a given hydroformylation reaction need only be thatminimum amount necessary to provide the given metal concentrationdesired to be employed and which will furnish the basis for at least thecatalytic amount of metal necessary to catalyze the particularhydroformylation reaction involved such as disclosed e.g. in theabove-mentioned patents. In general, the catalyst concentration canrange from several parts per million to several percent by weight.Organophosphorus ligands can be employed in the above-mentionedcatalysts in a molar ratio of generally from about 1:1 or less to about1000:1 or greater.

In general, the organophosphorus ligand concentration inhydroformylation reaction mixtures may range from between about 0.005and 15 weight percent based on the total weight of the reaction mixture.Preferably the ligand concentration is between 0.001 and 10 weightpercent, and more preferably is between about 0.05 and 5 weight percenton that basis.

In general, the concentration of the metal in the hydroformylationreaction mixtures may be as high as about 2000 parts per million byweight based on the weight of the reaction mixture. Preferably the metalconcentration is between about 50 and 1000 parts per million by weightbased on the weight of the reaction mixture, and more preferably isbetween about 70 and 800 parts per million by weight based on the weightof the reaction mixture.

In addition to the metal-organophosphorus ligand complex catalyst, freeorganophosphorus ligand (i.e., ligand that is not complexed with therhodium metal) is also present in the hydroformylation reaction medium.The free organophosphorus ligand may correspond to any of theabove-defined phosphorus-containing ligands discussed above asemployable herein. It is preferred that the free organophosphorus ligandbe the same as the phosphorus-containing ligand of themetal-organophosphorus complex catalyst employed. However, such ligandsneed not be the same in any given process. The hydroformylation reactionmay involve up to 100 moles, or higher, of free organophosphorus ligandper mole of metal in the hydroformylation reaction medium. Preferablythe hydroformylation reaction is carried out in the presence of fromabout 1 to about 50 moles of phosphorus-containing ligand, and morepreferably from about 1 to about 4 moles of phosphorus-containingligand, per mole of metal present in the reaction medium; said amountsof phosphorus-containing ligand being the sum of both the amount ofphosphorus-containing ligand that is bound (complexed) to the rhodiummetal present and the amount of free (non-complexed)phosphorus-containing ligand present. Of course, if desired, make-up oradditional phosphorus-containing ligand can be supplied to the reactionmedium of the hydroformylation reaction at any time and in any suitablemanner, e.g. to maintain a predetermined level of free ligand in thereaction medium.

The olefin starting material reactants that may be employed in thehydroformylation reactions include olefin compounds containing from 2 to30, preferably 3 to 20, carbon atoms. Such olefin compounds can beterminally or internally unsaturated and be of straight-chain, branchedchain or cyclic structures, as well as olefin mixtures, such as obtainedfrom the oligomerization of propene, butene, isobutene, etc. (such as socalled dimeric, trimeric or tetrameric propylene and the like, asdisclosed, e.g., in U.S. Pat. Nos. 4,518,809 and 4,528,403). Moreover,such olefin compounds may further contain one or more ethylenicunsaturated groups, and of course, mixtures of two or more differentolefinic compounds may be employed as the starting hydroformylationmaterial if desired. Further such olefin compounds and the correspondingaldehyde products derived therefrom may also contain one or more groupsor substituents which do not unduly adversely affect thehydroformylation process or the process of this invention such asdescribed, e.g., in U.S. Pat. Nos. 3,527,809; 4,668,651 and the like.

Illustrative olefinic unsaturated compounds are alpha-olefins, internalolefins, 1,3-dienes, alkyl alkenoates, alkenyl alkanoates, alkenyl alkylethers, alkenols, alkenals, and the like, e.g., ethylene, propylene,1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene,1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene,1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 2-butene,2-methyl propene (isobutylene), 2-methylbutene, 2-pentene, 2-hexene,3-hexane, 2-heptene, cyclohexene, propylene dimers, propylene trimers,propylene tetramers, butadiene, piperylene, isoprene, 2-ethyl-1-hexene,2-octene, styrene, 3-phenyl-l-propene, 1,4-hexadiene, 1,7-octadiene,3-cyclohexyl-1-butene, allyl alcohol, allyl butyrate, hex-1-en-4-ol,oct-1-en-4-ol, vinyl acetate, allyl acetate, 3-butenyl acetate, vinylpropionate, allyl propionate, methyl methacrylate, vinyl ethyl ether,vinyl methyl ether, allyl ethyl ether, methyl pentenoate,n-propyl-7-octenoate, pentenals, e.g., 2-pentenal, 3-pentenal and4-pentenal; pentenols, e.g., 2-pentenol, 3-pentenol and 4-pentenol;3-butenenitrile, 5-hexenamide, 4-methyl styrene, 4-isopropyl styrene,4-tert-butyl styrene, alpha-methyl styrene, 4-tert-butyl-alpha-methylstyrene, 1,3-diisopropenylbenzene, eugenol, iso-eugenol, safrole,iso-safrole, anethol, 4-allylanisole, indene, limonene, beta-pinene,dicyclopentadiene, cyclooctadiene, camphene, linalool, and the like.Other illustrative olefinic compounds useful in the hydroformylationreaction include, for example, p-isobutylstyrene,2-vinyl-6-methoxynaphthylene, 3-ethenylphenyl phenyl ketone,4-ethenylphenyl-2-thienylketone, 4-ethenyl-2-fluorobiphenyl,4-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)styrene,2-ethenyl-5-benzoylthiophene, 3-ethenylphenyl phenyl ether,propenylbenzene, isobutyl-4-propenylbenzene, phenyl vinyl ether and thelike. Other olefinic compounds include substituted aryl ethylenes asdescribed in U.S. Pat. No. 4,329,507, the disclosure of which isincorporated herein by reference.

Illustrative olefins useful in the hydroformylation reactions that canbe employed to produce aldehyde mixtures include those represented bythe formula: ##STR22## wherein R₁, R₂, R₃ and R₄ are the same ordifferent and are selected from hydrogen or a substituted orunsubstituted hydrocarbon radical, e.g., alkyl; substituted alkyl, saidsubstitution being selected from dialkylamino such as benzylamino anddibenzylamino, alkoxy such as methoxy and ethoxy, acyloxy such asacetoxy, halo, nitro, nitrile, thio, carbonyl, carboxamide,carboxaldehyde, carboxyl, carboxylic ester; aryl including phenyl;substituted aryl including phenyl, said substitution being selected fromalkyl, amino including alkylamino and dialkylamino such as benzylaminoand dibenzylamino, hydroxy, alkoxy such as methoxy and ethoxy, acyloxysuch as acetoxy, halo, nitrile, nitro, carboxyl, carboxaldehyde,carboxylic ester, carbonyl, and thio; acyloxy such as acetoxy; alkoxysuch as methoxy and ethoxy; amino including alkylamino and dialkylaminosuch as benzylamino and dibenzylamino; acylamino and diacylamino such asacetylbenzylamino and diacetylamino; nitro; carbonyl; nitrile; carboxyl;carboxamide; carboxaldehyde; carboxylic ester; and alkylmercapto such asmethylmercapto. It is understood that the olefins of this definitionalso include molecules of the above general formula where the R-groupsare connected to form ring compounds, e.g., 3-methyl-1-cyclohexene, andthe like.

Mixtures of different olefinic starting materials can be employed, ifdesired, in the hydroformylation reactions. More preferably thehydroformylation reactions are especially useful for the production ofaldehydes, by hydroformylating alpha olefins containing from 2 to 30,preferably 4 to 20, carbon atoms, including isobutylene, and internalolefins containing from 4 to 20 carbon atoms as well as startingmaterial mixtures of such alpha olefins and internal olefins. Commercialalpha olefins containing four or more carbon atoms may contain minoramounts of corresponding internal olefins and/or their correspondingsaturated hydrocarbon and that such commercial olefins need notnecessarily be purified from same prior to being hydroformylated.Illustrative mixtures of olefinic starting materials that can beemployed in the hydroformylation reactions include, for example, mixedbutenes, e.g., Raffinate I and II.

The hydroformylation reaction conditions may include any suitable typehydroformylation conditions heretofore employed for producing aldehydes.For instance, the total gas pressure of hydrogen, carbon monoxide andolefin starting compound of the hydroformylation process may range fromabout 1 to about 10,000 psia. In general, however, it is preferred thatthe process be operated at a total gas pressure of hydrogen, carbonmonoxide and olefin starting compound of less than about 1500 psia andmore preferably less than about 500 psia. The minimum total pressurebeing limited predominately by the amount of reactants necessary toobtain a desired rate of reaction. More specifically the carbon monoxidepartial pressure of the hydroformylation process of this invention ispreferable from about 1 to about 360 psia, and more preferably fromabout 3 to about 270 psia, while the hydrogen partial pressure ispreferably about 15 to about 480 psia and more preferably from about 30to about 300 psia. In general, the molar ratio of gaseous hydrogen tocarbon monoxide may range from about 1:10 to 100:1 or higher, the morepreferred hydrogen to carbon monoxide molar ratio being from about 1:1to about 10:1. Further, the hydroformylation process may be conducted ata reaction temperature from about -25° C. to about 200° C. In generalhydroformylation reaction temperature of about 50° C. to about 120° C.are preferred for all types of olefinic starting materials. Of course,it is to be also understood that the hydroformylation reactionconditions employed will be governed by the type of aldehyde productdesired.

The hydroformylation reaction is also conducted in the presence of anorganic solvent for the metal-organophosphorus complex catalyst and freeorganophosphorus ligand. Depending on the particular catalyst andreactants employed, suitable organic solvents include, for example,alcohols, alkanes, alkenes, alkynes, ethers, aldehydes, higher boilingaldehyde condensation by-products, ketones, esters, amides, tertiaryamines, aromatics and the like. Any suitable solvent which does notunduly adversely interfere with the intended hydroformylation reactioncan be employed and such solvents may include those disclosed heretoforecommonly employed in known metal catalyzed hydroformylation reactions.Mixtures of one or more different solvents may be employed if desired.In general, with regard to the production of aldehydes, it is preferredto employ aldehyde compounds corresponding to the aldehyde productsdesired to be produced and/or higher boiling aldehyde liquidcondensation by-products as the main organic solvents as is common inthe art. Such aldehyde condensation by-products can also be preformed ifdesired and used accordingly. Illustrative preferred solvents employablein the production of aldehydes include ketones (e.g. acetone andmethylethyl ketone), esters (e.g. ethyl acetate), hydrocarbons (e.g.toluene), nitrohydrocarbons (e.g. nitrobenzene) and ethers (e.g.tetrahydrofuran (THF) and glyme). Suitable solvents are disclosed inU.S. Pat. No. 5,312,996. The amount of solvent employed is not criticalto the subject invention and need only be that amount sufficient tosolubilize the catalyst and free ligand of the hydroformylation reactionmixture to be treated. In general, the amount of solvent may range fromabout 5 percent by weight up to about 99 percent by weight or more basedon the total weight of the hydroformylation reaction mixture startingmaterial.

Illustrative aldehyde products include e.g., propionaldehyde,n-butyraldehyde, isobutyraldehyde, n-valeraldehyde,2-methylbutyraldehyde, hexanal, 2-methylvaleraldehyde, heptanal,2-methylhexanal, octanal, 2-methylheptanal, nonanal, 2-methyloctanal,2-ethylheptanal, 2-propylheptanal, 3-propylhexanal, decanal,adipaldehyde, 2-methylglutaraldehyde, 2-methyladipaldehyde,3-methyladipaldehyde, 3-hydroxypropionaldehyde, 3-pentenal, alkyl5-formylvalerate, 2-methylnonanal, undecanal, 2-methyldecanal,dodecanal, 2-methylundecanal, tridecanal, 2-methyltridecanal,2-ethyldodecanal, 3-propylundecanal, pentadecanal, 2-methyltetradecanal,hexadecanal, 2-methylpentadecanal, heptadecanal, 2-methylhexadecanal,octadecanal, 2-methylheptadecanal, nonodecanal, 2-methyloctadecanal,2-ethylheptadecanal, 3-propylhexadecanal, eicosanal,2-methylnonadecanal, heneicosanal, 2-methyleicosanal, tricosanal,2-methyldocosanal, tetracosanal, 2-methyltricosanal, pentacosanal,2-methyltetracosanal, 2-ethyltricosanal, 3-propyldocosanal,heptacosanal, 2-methyloctacosanal, nonacosanal, hentriacontanal,2-methyltriacontanal, and the like.

As indicated above, the hydroformylation reactions may involve a liquidcatalyst recycle procedure. Such liquid catalyst recycle procedures areknown as seen disclosed, e.g., in U.S. Pat. Nos. 4,668,651; 4,774,361;5,102,505 and 5,110,990. For instance, in such liquid catalyst recycleprocedures it is common place to continuously or intermittently remove aportion of the liquid reaction product medium, containing, e.g., thealdehyde product, the solubilized metal-organophosphorus complexcatalyst, free ligand, and organic solvent, as well as by-productsproduced in situ by the hydroformylation, e.g., aldehyde condensationby-products etc., and unreacted olefinic starting material, carbonmonoxide and hydrogen (syn gas) dissolved in said medium, from thehydroformylation reactor, to a distillation zone, e.g., avaporizer/separator wherein the desired aldehyde product is distilled inone or more stages under normal, reduced or elevated pressure, asappropriate, and separated from the liquid medium. The vaporized ordistilled desired aldehyde product so separated may then be condensedand recovered in any conventional manner as discussed above. Theremaining non-volatilized liquid residue which containsmetal-organophosphorus complex catalyst, solvent, free organophosphorusligand and usually some undistilled aldehyde product is then recycledback, with or with out further treatment as desired, along with whateverby-product and non-volatilized gaseous reactants that might still alsobe dissolved in said recycled liquid residue, in any conventional mannerdesired, to the hydroformylation reactor, such as disclosed e.g., in theabove-mentioned patents. Moreover the reactant gases so removed by suchdistillation from the vaporizer may also be recycled back to the reactorif desired.

In an embodiment of this invention, the aldehyde mixtures may beseparated from the other components of the crude reaction mixtures inwhich the aldehyde mixtures are produced by any suitable method.Suitable separation methods include, for example, solvent extraction,crystallization, distillation, vaporization, wiped film evaporation,falling film evaporation and the like. It may be desired to remove thealdehyde products from the crude reaction mixture as they are formedthrough the use of trapping agents as described in published PatentCooperation Treaty Patent Application WO 88/08835. A preferred methodfor separating the aldehyde mixtures from the other components of thecrude reaction mixtures is by membrane separation. Such membraneseparation can be achieved as set out in U.S. Pat. No. 5,430,194 andcopending U.S. patent application Ser. No. 08/430,790, filed May 5,1995, both incorporated herein by reference.

More particularly, distillation and separation of the desired aldehydeproduct from the metal-organophosphorus complex catalyst containingproduct solution may take place at any suitable temperature desired. Ingeneral, it is recommended that such distillation take place atrelatively low temperatures, such as below 150° C., and more preferablyat a temperature in the range of from about 50° C. to about 130° C. Itis also generally recommended that such aldehyde distillation take placeunder reduced pressure, e.g., a total gas pressure that is substantiallylower than the total gas pressure employed during hydroformylation whenlow boiling aldehydes (e.g., C₄ to C₆) are involved or under vacuum whenhigh boiling aldehydes (e.g. C₇ or greater) are involved. For instance,a common practice is to subject the liquid reaction product mediumremoved from the hydroformylation reactor to a pressure reduction so asto volatilize a substantial portion of the unreacted gases dissolved inthe liquid medium which now contains a much lower synthesis gasconcentration than was present in the hydroformylation reaction mediumto the distillation zone, e.g. vaporizer/separator, wherein the desiredaldehyde product is distilled. In general, distillation pressuresranging from vacuum pressures or below on up to total gas pressure ofabout 50 psig should be sufficient for most purposes.

The generic scope of this invention includes a process for preparingcarboxylic acids by oxidizing an aldehyde with a peracid in the presenceof an amine and/or amine N-oxide catalyst to produce the carboxylicacid. The generic scope of this invention is not intended to be limitedin any manner by any particular aldehyde-forming reaction.

Oxidation

Other aldehydes which may be useful in the process of this inventioninclude, for example, 2-phenylpropionaldehyde,2-(p-isobutylphenyl)propionaldehyde,2-(6-methoxy-2-naphthyl)propionaldehyde,2-(3-benzoylphenyl)-propionaldehyde,2-(p-thienoylphenyl)propionaldehyde,2-(3-fluoro-4-phenyl)phenylpropionaldehyde, 2-4-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)phenyl!propionaldehyde,2-(2-methylacetaldehyde)-5-benzoylthiophene and the like. Illustrativeof suitable aldehyde (including derivatives of aldehydes) and olefinstarting material compounds include those permissible aldehyde andolefin starting material compounds which are described in Kirk-Othmer,Encyclopedia of Chemical Technology, Third Edition, 1984, the pertinentportions of which are incorporated herein by reference.

Once the requisite aldehyde product has been provided, the next step ofthe process of this invention involves oxidizing the aldehyde with aperacid in the presence of an amine and/or amine N-oxide catalyst toproduce a carboxylic acid. Suitable solutions can be provided by usingliquid aldehydes or by melting solid aldehydes. However, suitablesolutions usually consist of the aldehydes dissolved in an appropriatesolvent (e.g., in the solvent in which the first step of the process ofthis invention was conducted). Any solvent which will dissolve thealdehyde product and is unreactive with peracids may be used. Examplesof suitable solvents are ketones (e.g., acetone), esters (e.g., ethylacetate), hydrocarbons (e.g., toluene), nitrohydrocarbons (e.g.,nitrobenzene), ethers (e.g., tetrahydrofuran (THF) and1,2-dimethoxyethane) and water. A mixture of two or more solvents can beemployed to maximize the purity and yield of the desired aldehyde. Thesolution used may also contain materials present in the crude reactionproduct of the aldehyde-forming reaction (e.g., catalyst, ligand andheavies). Preferably, however, the solution consists essentially of onlythe aldehyde and the solvent. The concentration of the aldehyde in thesolvent solution will be limited by the solubility of the aldehyde inthe solvent.

The oxidizing agent useful in the process of this invention is aperacid. Illustrative peracids include, for example, peracetic acid,performic acid, perpropionic acid, perbenzoic acid and the like. Thepreferred oxidizing agent is anhydrous peracetic acid. Such peracidoxidizing agents are well known in the art and can be used in amountsdescribed below and in accordance with conventional methods.

The oxidizing agent is employed in an amount sufficient to permitcomplete oxidation of the aldehyde. Preferably, the oxidizing agentstoichiometry can range from about 1 to about 10 molar equivalents withrespect to aldehyde, preferably from about 1 to about 2 molarequivalents with respect to aldehyde, and most preferably from about 1to about 1.3 molar equivalents with respect to aldehyde.

The catalysts useful in the oxidation step of the process of thisinvention include primary, secondary and tertiary amines and amineN-oxides and mixtures thereof. The catalysts have sufficient basicity tocatalyze the oxidation of an aldehyde to a carboxylic acid. Illustrativeprimary, secondary and tertiary amine and amine N-oxide catalystsinclude, for example, aliphatic amines, aliphatic amine N-oxides,aromatic amines, aromatic amine N-oxides, heterocyclic amines,heterocyclic amine N-oxides, polymeric amines, polymeric amine N-oxidesand the like, including mixtures thereof. Illustrative aliphatic aminesinclude substituted and unsubstituted alkyl amines such as butylamine,diethylamine, triethylamine and the like including the N-oxides thereof.Illustrative aromatic amines (those in which nitrogen is attacheddirectly to an aromatic ring) include substituted and unsubstitutedanilines and the N-oxides thereof, e.g., aniline, toluidine,diphenylamine, N-ethyl-N-methylaniline, 2,4,6-tribromoaniline and thelike. Illustrative heterocyclic amines (those in which nitrogen makes upa part of an aromatic or non-aromatic ring) include substituted andunsubstituted pyridines, pyrimidines, pyrrolidines, piperidines,pyrroles, purines and the like including the N-oxides thereof. Preferredoxidation catalysts include, for example, 2,6-lutidine N-oxide,5-ethyl-2-methylpyridine, 5-ethyl-2-methylpyridine N-oxide,4-methoxypyridine N-oxide and 2,5-1utidine N-oxide. Amine N-oxidecatalysts are preferred oxidation catalysts and can affect, e.g.,decrease, the amount of formate byproduct formed in the oxidationprocess of this invention. The amine and/or amine N-oxide catalystpreferably has a high boiling point so as to reduce or eliminate amineimpurities resulting from the catalyst in the product.

As indicated above, the catalysts have sufficient basicity to catalyzethe oxidation of an aldehyde to a carboxylic acid. Such basicity canresult from the catalyst functioning as a Lewis base or a Bronsted-Lowrybase. The catalysts should be basic enough to promote decomposition ofany aldehyde-peracid adduct but relatively unreactive with regard tooxidation by peracid. The basicity of the catalysts should also besufficient to favor the oxidation reaction to carboxylic acids over anycompeting aldehyde reactions.

The amine and/or amine N-oxide catalyst is employed in a catalyticallyeffective amount, i.e., an amount sufficient to catalyze the oxidationreaction. Preferably, the amine and/or amine N-oxide stoichiometry canrange from about 0.1 to about 10 molar equivalents with respect toaldehyde, preferably from about 0.5 to about 2 molar equivalents withrespect to aldehyde, and most preferably from about 0.7 to about 1.2molar equivalents with respect to aldehyde. The amine and/or amineN-oxide stoichiometry can affect the amount of formate byproduct formedin the process of this invention.

The catalysts used in the oxidation step of the process of thisinvention may optionally be supported. Advantages of a supportedcatalyst may include ease of catalyst separation. Illustrative examplesof supports include alumina, silica gel, ion-exchange resins, polymericsupports and the like.

The process conditions employable in the oxidation step of the processof this invention are chosen to reduce formate byproducts.

The mode of addition of reaction ingredients in the oxidation step ofthe process of this invention is not narrowly critical. The mode ofaddition should be such that an carboxylic acid is obtained.

The oxidation step of the process of this invention may be conducted ata reaction temperature from about -25° C. or lower to about 60° C. Lowerreaction temperatures may generally tend to minimize formate byproductformation. When using amine N-oxides as catalysts, temperatures shouldnot exceed about 25° C. to minimize methyl ketone formation whenoxidizing alpha-methyl substituted benzylic aldehydes. In general,oxidations at reaction temperatures of about -10° C. to about 25° C. arepreferred.

The oxidation step of the process of this invention is conducted for aperiod of time sufficient to produce a carboxylic acid. The exactreaction time employed is dependent, in part, upon factors such astemperature, nature and proportion of starting materials, and the like.The reaction time will normally be within the range of from aboutone-half to about 200 hours or more, and preferably from less than aboutone to about 10 hours.

The oxidation step in the process of this invention can be carried outin the liquid state and can involve a batch or continuous liquid recyclesystem. A batch system is preferred for conducting such processes.Preferably, such oxidation involves a batch homogeneous catalysisprocess wherein the oxidation is carried out in the presence of anysuitable conventional solvent as further described herein.

The oxidation step of the process of this invention may be conducted inthe presence of an organic solvent. Depending on the particular catalystand reactants employed, suitable organic solvents include, for example,alcohols, alkanes, ethers, aldehydes, esters, acids, amides, amines,aromatics and the like. Any suitable solvent which does not undulyadversely interfere with the intended oxidation process can be employedand such solvents may include those heretofore commonly employed inknown processes. Mixtures of one or more different solvents may beemployed if desired. Solvents which partially or totally dissolve thealdehyde and do not react with peracids may be useful. Organic estersare preferred solvents. Water and water/ethanol mixtures may also beuseful solvents. The amount of solvent employed is not critical to thisinvention and need only be that amount sufficient to provide thereaction medium with the particular substrate and product concentrationdesired for a given process. In general, the amount of solvent whenemployed may range from about 5 percent by weight up to about 95 percentby weight or more based on the total weight of the reaction medium.

As indicated above, the carboxylic acid-forming process of thisinvention can be conducted in a batch or continuous fashion, withrecycle of unconsumed starting materials if required. The reaction canbe conducted in a single reaction zone or in a plurality of reactionzones, in series or in parallel or it may be conducted batchwise orcontinuously in an elongated tubular zone or series of such zones. Thematerials of construction employed should be inert to the startingmaterials during the reaction and the fabrication of the equipmentshould be able to withstand the reaction temperatures and pressures.Means to introduce and/or adjust the quantity of starting materials oringredients introduced batchwise or continuously into the reaction zoneduring the course of the reaction can be conveniently utilized in theprocesses especially to maintain the desired molar ratio of the startingmaterials. The reaction steps may be effected by the incrementaladdition of one of the starting materials to the other. Also, thereaction steps can be combined by the joint addition of the startingmaterials to the amine and/or amine N-oxide catalyst. The processes maybe conducted in either glass lined, stainless steel or similar typereaction equipment. The reaction zone may be fitted with one or moreinternal and/or external heat exchanger(s) in order to control unduetemperature fluctuations, or to prevent any possible "runaway" reactiontemperatures.

The carboxylic acid-forming process of this invention is useful forpreparing mixtures of substituted and unsubstituted carboxylic acids.Illustrative preferred carboxylic acids prepared by the oxidationprocess of this invention include, for example, 2-phenylpropionic acid,2-(p-isobutylphenyl)propionic acid, 2-(6-methoxy-2-naphthyl)propionicacid, 2-(3-benzoylphenyl)propionic acid, 2-(p-thienoylphenyl)propionicacid, 2-(3-fluoro-4-phenyl)phenylpropionic acid, 2-4-(1,3-dihydro-l-oxo-2H-isoindol-2-yl)phenyl!propionic acid and thelike. Illustrative of suitable carboxylic acids which can be prepared bythe processes of this invention include those permissible carboxylicacids which are described in Kirk-Othmer, Encyclopedia of ChemicalTechnology, Third Edition, 1984, the pertinent portions of which areincorporated herein by reference.

The carboxylic acids described herein is useful in a variety ofapplications, such as intermediates in the manufacture of chemicalcompounds, pharmaceutical manufacture and the like.

For purposes of this invention, the term "hydrocarbon" is contemplatedto include all permissible compounds having at least one hydrogen andone carbon atom. In a broad aspect, the permissible hydrocarbons includeacyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic organic compounds which can besubstituted or unsubstituted.

As used herein, the term "substituted" is contemplated to include allpermissible substituents of organic compounds unless otherwiseindicated. In a broad aspect, the permissible substituents includeacyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic substituents of organiccompounds. Illustrative substituents include, for example, alkyl,alkyloxy, aryl, aryloxy, hydroxy, hydroxyalkyl, amino, aminoalkyl,halogen and the like in which the number of carbons can range from 1 toabout 20 or more, preferably from 1 to about 12. The permissiblesubstituents can be one or more and the same or different forappropriate organic compounds. This invention is not intended to belimited in any manner by the permissible substituents of organiccompounds.

For purposes of this invention, the chemical elements are identified inaccordance with the Periodic Table of the Elements, CAS version,Handbook of Chemistry and Physics, 67th Ed., 1986-87, inside cover.

As used herein, the following symbols have the indicated meanings:

    ______________________________________                                               mL         milliliter                                                         g          grams                                                              °C. degrees centigrade                                                 mmol       millimoles                                                         min        minute                                                      ______________________________________                                    

The following example is provided to illustrate the process of thisinvention.

EXAMPLE 1 Oxidation Of Cyclohexanecarboxaldehyde ToCyclohexanecarboxylic Acid Using Lutidine N-Oxide As Catalyst

To a stirred solution of 5.0 g (44.6 mmol) of cyclohexanecarboxaldehydein n-butyl acetate (45 mL) cooled in a wet-ice bath (ca. 2° C.) wasadded 5.5 g (44.6 mmol) of 2,6-dimethylpyridine N-oxide (2,6-lutidineN-oxide). To this solution was then added slowly dropwise 24.6 mL (66.9mmol) of a 23.0 weight percent solution of peracetic acid in ethylacetate, at a rate slow enough such that the reaction temperature didnot exceed 10° C. (ca. 20 min). After the initial exotherm, thetemperature returned to 2° C., and the reaction was maintained at thistemperature for an additional 4 hours. The cold reaction solution wasthen transferred into a separatory funnel, was diluted with n-butylacetate (50 mL), and was washed with a 1% aqueous solution of sodiumthiosulfate (Na₂ S₂ O₃, 50 mL). The butyl acetate layer was furtherwashed with two portions of water (50 mL each), and the combined waterwashes were back-extracted with n-butyl acetate (50 mL). The combinedbutyl acetate layers were extracted with two portions of a 5% aqueoussolution of sodium hydroxide (NaOH, 50 mL each). The combined NaOHsolutions were acidified to pH=1 with a 10% aqueous solution ofhydrochloric acid. The resulting solution was extracted with twoportions of dichloromethane (75 mL each), and the extract was dried overanhydrous Na₂ SO₄. The extract was filtered and concentrated in vacuo togive 6.0 g (99%) of cyclohexanecarboxylic acid, containing small levelsof unidentified impurities.

Although the invention has been illustrated by the preceding example, itis not to be construed as being limited thereby; but rather, theinvention encompasses the generic area as hereinbefore disclosed.Various modifications and embodiments can be made without departing fromthe spirit and scope thereof.

We claim:
 1. A process for producing a carboxylic acid which process comprises oxidizing an aldehyde with a peracid in the presence of an amine and/or amine N-oxide catalyst selected from the group consisting of a substituted or unsubstituted alkyl amine, alkyl amine N-oxide, aromatic amine, aromatic amine N-oxide, heterocyclic amine, heterocyclic amine N-oxide and mixtures thereof, to produce the carboxylic acid, wherein said amine and/or amine N-oxide catalyst has a basicity sufficient to catalyze said oxidizing of the aldehyde to the carboxylic acid, and provided that when the peracid is performic acid, the aldehyde is other than an aromatic or heteroaromatic aldehyde.
 2. The process of claim 1 in which the aldehyde is selected from 2-phenylpropionaldehyde, 2-(p-isobutylphenyl)propionaldehyde, 2-(6-methoxy-2-naphthyl)propionaldehyde, 2-(3-benzoylphenyl)-propionaldehyde, 2-(p-thienoylphenyl)propionaldehyde, 2-(3-fluoro-4-phenyl)phenylpropionaldehyde, 2-propionaldehyde and 2-(2-methylacetaldehyde)-5-benzoylthiophene.
 3. The process of claim 1 in which the peracid is selected from peracetic acid, performic acid, perpropionic acid and perbenzoic acid.
 4. The process of claim 1 in which the amine and/or amine N-oxide catalyst is selected from 2,6-lutidine N-oxide, 5-ethyl-2-methylpyridine, 5-ethyl-2-methylpyridine N-oxide, 4-methoxypyridine N-oxide and 2,5-lutidine N-oxide.
 5. The process of claim 1 in which the carboxylic acid is selected from 2-phenylpropionic acid, 2-(p-isobutylphenyl)propionic acid, 2-(6-methoxy-2-naphthyl)propionic acid, 2-(3-benzoylphenyl)propionic acid, 2-(p-thienoylphenyl)propionic acid, 2-(3-fluoro-4-phenyl)phenylpropionic acid and 2-propionic acid. 